Tuning Reactivity of Platinum(II) Complexes
Tuning Reactivity of Platinum(II) Complexes Tuning Reactivity of Platinum(II) Complexes
List of Tables Table 5.1: A summary of DFT-calculated parameters for the aqua complexes pzn to pht. The table is ordered according to increasing values of Natural Atomic charges (NBO) of Pt(II) centres. ........................................................................................................................................................ 10 Table 5.2 : Acid dissociation constants of platinum(II) complexes determined spectrophotometrically at 25 °C (Ionic strength, I = 0.1 M NaClO4/ HClO4). ....................... 14 Table 5.3: A summary of DFT calculated Parameters for aqua/hydroxo complex systems of benzodiazines and their monocyclic analogues. ............................................................................ 16 Table 5.4: Summary of second order rate constants of diazine-bridged dinuclear Pt(II) complexes; I = 0.1 M (NaClO4, adjusted with HClO4), T = 298.15 K. ........................................... 23 Table 5.5: Summary of Activation parameters for the displacement of coordinated water by a series of nucleophiles in complexes of the Type [cis-{PtOH2(NH3)2-μ-pzn] 4+, I = 0.1 M NaClO4. ................................................................................................................................................................ 27 iii
Chapter 5 Substitution Reactions in Dinuclear Platinum(II) Complexes: an Evaluation of the Influence of the Diazine-bridge on Reactivity 5.0 Abstract The kinetics of substitution reactions of aqua dinuclear Pt(II) complexes, [{cis– Pt(OH2)(NH3)2}2–μ–pmn](ClO4)2 (pmn), [{cis–Pt(OH2)(NH3)2}2–μ–pdn](ClO4)2 (pdn), [{cis–Pt(OH2)(NH3)2}2–μ–qzn](ClO4)2 (qzn), [{cis–Pt(OH2)(NH3)2}2–μ– pht](ClO4)2 (pht), and [{cis–Pt(OH2)(NH3)2}2–μ–pzn](ClO4)2 (pzn) (pmn = pyrimidine, pdn = pyridazine, qzn = quinazoline, pht = phthalazine, pzn = pyrazine) and sulphur-donor nucleophiles, viz. thiourea (TU), N,N–dimethylthiourea (DMTU) and N,N,N,N–tetramethylthiourea (TMTU) were investigated. The reactions were followed under pseudo first-order conditions as a function of nucleophile concentration and temperature using stopped-flow and UV-Vis Spectrophotometric methods. The reactivity of the nucleophiles follows the order TU > DMTU > TMTU. The results of the rate constants for the consecutive substitution of the aqua ligand showed that pzn is more reactive than the rest of dinuclear complexes. The reactivity of the aqua complexes follows the order pzn > qzn > pmn > pdn > pht which was confirmed by the quantum chemical (DFT) NBO charges and the pKa calculations. The results indicate that changing the position or distance of the N atoms of the bridging ligand controls the electrophilicity of the metal centre and hence its reactivity. The results further indicate that the metal centre is activated differently in the cases of qzn and pht, even though both are part of a π–conjugated system. The negative values reported for the activation entropy confirm the associative nature of substitution process. 1H NMR was used to follow the substitution of the aqua ligand by excess thiourea and confirmed the displacement of the bridging ligand in the third step in all cases. The results clearly demonstrate a strong connection between the reactivity of the dinuclear Pt(II) complexes with sulphur nucleophiles and their structural and electronic characteristics. 1
- Page 166 and 167: k obs(3 rd ) , s -1 -5 6.00x10 TMTU
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- Page 170 and 171: ln([ML] t ) 4.0 3.5 3.0 2.5 2.0 1.5
- Page 172 and 173: ln(k 2(1 st ) /T) -3.5 -4.0 -4.5 -5
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- Page 180 and 181: eaction proceeds via bimolecular pa
- Page 182 and 183: References 1 T. Storr, K. H.Thomson
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- Page 186 and 187: Appendix 4 THE INFLUENCE OF THE PYR
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- Page 192 and 193: k nd obs(2 ) , s-1 0.003 TU DMTU TM
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- Page 198 and 199: k obs2 , s -1 2.40x10 -4 2.20x10 -4
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- Page 204 and 205: Table S4.18: Average observed rate
- Page 206 and 207: k obs(1 st ) , s -1 0.06 0.04 0.02
- Page 208 and 209: Table S4.23: Average observed rate
- Page 210 and 211: ln(k 2(3 rd ) /T) -10.0 -10.5 -11.0
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- Page 234 and 235: H3N 6 eq TU 0 eq TU Ha NH3 Ha Cl TU
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- Page 240 and 241: k obs(1st) / s -1 0.20 TU DMTU TMTU
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- Page 244 and 245: ln(k st 2(1 ) /T) -3 -4 -5 -6 -7 -8
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- Page 256 and 257: k obs(1 st ) , s -1 0.4 0.3 0.2 0.1
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- Page 260 and 261: ln(k 2(2 nd ) /T) -8.0 TU -8.5 -9.0
- Page 262 and 263: pzn PPM -1750.0 -1850.0 -1950.0 -20
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List <strong>of</strong> Tables<br />
Table 5.1: A summary <strong>of</strong> DFT-calculated parameters for the aqua complexes pzn to pht.<br />
The table is ordered according to increasing values <strong>of</strong> Natural Atomic charges (NBO) <strong>of</strong><br />
Pt(<strong>II</strong>) centres. ........................................................................................................................................................ 10<br />
Table 5.2 : Acid dissociation constants <strong>of</strong> platinum(<strong>II</strong>) complexes determined<br />
spectrophotometrically at 25 °C (Ionic strength, I = 0.1 M NaClO4/ HClO4). ....................... 14<br />
Table 5.3: A summary <strong>of</strong> DFT calculated Parameters for aqua/hydroxo complex systems<br />
<strong>of</strong> benzodiazines and their monocyclic analogues. ............................................................................ 16<br />
Table 5.4: Summary <strong>of</strong> second order rate constants <strong>of</strong> diazine-bridged dinuclear Pt(<strong>II</strong>)<br />
complexes; I = 0.1 M (NaClO4, adjusted with HClO4), T = 298.15 K. ........................................... 23<br />
Table 5.5: Summary <strong>of</strong> Activation parameters for the displacement <strong>of</strong> coordinated water<br />
by a series <strong>of</strong> nucleophiles in complexes <strong>of</strong> the Type [cis-{PtOH2(NH3)2-μ-pzn] 4+, I = 0.1<br />
M NaClO4. ................................................................................................................................................................ 27<br />
iii
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